Work on and in rock walls often results in problems involving moisture and water that penetrates through cracks in the rock, which often requires the cracks to be sealed. Leakages also often occur in the vicinity of holes drilled with the intention of strengthening the rock wall, as a result of having punctured the natural existing rock screen. Sealing of the hole is often effected by injecting some type of sealant into the drilled holes. Examples of such sealants include cement grout or concrete injected into the hole. However, these sealants are unable to penetrate out into the actual cracks to any appreciable extent, wherewith the leakage problems remain in many instances. Another known rock sealing method requires coating the inside of the rock wall with concrete or some other appropriate material for instance.
It is not permitted in several cases to fasten reinforcing bolts in water-seeping holes, it being necessary to first ensure that the hole is dry.
A so-called packer is normally used for injecting a sealant or filler into a hole in a rock wall. A packer normally includes a tubular part that is fitted to the end of a tubular drill bit or to a conduit for delivering some type of sealant, and an expandable cuff, for instance made of rubber material, disposed on the tubular part of the packer. When this cuff is caused to expand the packer will be firmly affixed to the inside of the hole by means of friction, therewith tightening the packer against the walls of the hole. The sealant which is then injected into the hole is therefore unable to run out of the hole provided that the packer remains in the hole with the sealing medium still in a liquid state.
One known type of packer is expanded with the aid of the sealant later used to seal the hole. The sealant is advanced to the packer, where it is first conducted out to the surrounding cuff, causing the same to expand. When this has taken place, the pressure exerted by the sealant will cause a bursting disk or some corresponding device included in the packer to burst, so that the sealant is able to penetrate past the packer and out into the rearward lying hole. The packer is normally left in the hole upon completion of the injection phase and when the sealant has hardened since the packer is usable only once and can not therefore be re-used. Consequently, this type of packer is expensive, since it is designed for one-time-use only.
Another known type of packer is expanded with the aid of a pneumatic or hydraulic pressure medium. This requires the application of a separate tool to the packer at the hole opening. The disadvantage of this type of packer is that it can only be used in the close vicinity of the hole opening, since the tool is relatively unwieldy and space-demanding. Because the packer cannot be inserted further into the hole, there is a risk that sealant can not be forced right down to the bottom of the hole and out into those cracks situated at the hole bottom. This may well result in an empty space behind the filling material, with the risk of this space being filled with water. This water will then exert a pressure on the injected filling material, which normally shrinks slightly after hardening and which will not therefore adhere fully to the hole walls, which can result in the entire “plug” of filler material releasing its grip on the hole as a result of water leakage, and sometimes even falling out of the hole.